Method of refining glass



J. W. WRIGHT METHOD OF REFINING GLASS Filed Sept INVENTOR :Eseph WWI"[16,

ATTORN EYS Patented on. 16, 1945 METHOD OF REFINING GLASS Joseph w.Wright, Alton, 111., assignor to Owens- Illinois Glass Company, acorporation of Ohio Application September 17, 1941, Serial No. 411,170

6 Claims. (01. 49-54) My invention relates to a novel method andapparatus for use in the process of melting and refining glass and othermaterials. The invention is particularly adapted for use in connectionwith so-called continuous tanks in which the operations of meltingandrefining glass are carried on continuously. Such tanks are usually oflarge capacity, containing many tons of the material Heat for meltingthe batch is applied in the form of flames which is being melted andrefined.

or gases of combustion applied to the surface of the material. The rawbatch is introduced at one end of the tank and is gradually melted andrefined as it; advances slowly lengthwise of the tank In the meltingprocess alarge number of minute gas bubbles are introduced or generatedwithin the mass of viscous material and these must be eliminated beforethe glass is in suitable condition for use. Owing .to the viscous natureof the glass, the upward movement of these seeds to the surface is slow.In the melting operation convection currents are set up through the massand these tend to produce cords or streaks throughout the glass which,unless eliminated, result in defective ware. It is also necessary toreduce'the molten material to a uniform homo-' geneous consistencybefore it is suitable for the manufacture of commercial ware.

An object of my invention is to provide a novel method and means forfacilitating the melting and refining operations by producing acontrolled circulation or movement of the glass in the tank in a mannerto control the convection currents, produce a comparatively rapiddischarge of the seeds or bubbles, and promote a better homogeneity ofthe glass. v

A more specific object of the invention is to provide a method andapparatus for introducing a gas or gas-forming material into'the meltingvection currents of the molten material within the furnace and suchchanges are accompanied with changes. in the homogeneity of the glass.An object of the present invention-is to control the convection currentsand the .movement of glass within the tank ina manner to reduce oreliminate such changes in the homogeneity and produce a glass which isuniform throughout. In furnaces where convection currents are controlledprimarily by heat distribution, the surface glass near the discharge endof the furnace has been found periodically to contain an excess ofsilica and a deficiency in the balance of 'the glass constituents. Anobject of my invention is to provide means for controlling theconvection currentsin such a manner that an excess of silica inthesurface glass near the discharge end of tank, preferably through thefloor thereof, and V the mass and materially reduce the amount of fuelrequired.

In the melting of glass in tank furnaces'the quantity of molten glassdrawn from the furnace and likewise the quantity of batch materials fedinto the furnace vary in amount, depending upon thesize and weight ofglass articles being manufactured or the number of blowing machinesdrawing glass from the tank. This variation in, therate of meltingcauses changes in the conthe tank is prevented and a more homogeneousFig. 4 is an enlarged view showing the end portion of the pipe shown inFig. 3.

The tank, which may be of conventionalconstruction, comprises a floorl0, side walls H, a roof l2, and end walls I3 and Hi, all made ofrefractory material. The furnace may be supported as usual by a metalframework or structure IS. A bridge wall It separates the main ormelting compartment I! from the conditioning or refining compartment l8,said compartments being in communication through a conduit l9 extendingbeneath thebridge wall. The raw batch mate-- rials may be introducedthrough openings in the end wall [3 and are melted and refined to someextent as they advance slowly through the compartment H. The moltenmetal then passes through the conduit l9 into the conditioning chamberl8 where it isfurther refined and conditioned before it is withdrawn ordischarged from the tank.. Heat for melting the glass is supplied fromregenerators 20 from which hot gases are discharged through ports 2]which open into the melting compartment above the level of the glass,said ports being arranged at intervals along both sides or the furnace.The furnace as above described is or well known construction and is notper se a part of the present invention. In accordance with my inventionI provide a;

series of pipes 22 or gas line which lead to and I extend upwardlythrough the door oi the iurnace shown in Figs. 3 and 4 the pipesterminate at the door surface. "Within each metal pipe is a refractorymaterial 28 formed with a central opening or passageway 3|! throughwhich the gas is conducted into the furnace.

The gasas it flows upward through the passageway I0 formsa bubble 31within the molten glass at the mouth of the tube, the size' oi thebubble being dependent primarily on the surface tension of the glass andin a measure on the shape or the tube'or conduit at its discharge end.When the bubble reaches a certain size it will break loose from the endof the tube and commence to rise toward the surface of the glass.

This upward movement or the :bubble causes the comparatively viscousmetal which envelope it to Q move upward therewith. This upward pull ormovement of the glass is confined mainly to the portion thereofimmediately adjoining the bubble.

assaaaa v or glass in accordance with the present invention alsoaccelerates the melting and refining operations and results in asubstantial saving in dual and increasedmelting capacity. I

The gas bubbles which are liberated within the glass in accordance withthe'present invention are comparatively large and break immediately.upon reaching the suriace oi the glass, and hence do not introduce smallseeds or bubbles into the molten mass. The particular type of gas usedmay vary, depending on whether it is, desired to use an oxidizing, areducingor a neutral gas for the purpose oi. reacting on the glass. Forexample, where the glass batch contains iron, an oxidizing gas may beused for oxidising the iron. A reducing gas may be used to retaincertain coloring compounds. A neutral gas may be employed where it isdesired to avoid any changesin the state of the chemical contentscomprised for example, water, ammonium nitrate,am-

monidm sulphate, sodium chloride," arsenic and The gas supplied byeachpipeis liberated within the glass in a succession of bubbles 3! formedat intervals which ma be controlled and regulated by regulating thepressure of the gas. These bubbles, which may be substantially sphericalwhen released from the pipe 22, gradually expand as they rise and arealso flattened out before they are discharged atthe surface of theglass.

other materials which readily form gas, may be satisfactorily used wheresuch materials are delivered under properl controlled conditions.

Referring to Fig. '1, air or other gas may be suppliednnder pressurethrough a pressure pipe 35, reducing valve as and a pipe 3? to manifoldpipes 38. The manifold pipes are in oommunication with the pipe lines 22through sealed containers or bubbling tubes is individual to saidlines.- Each container is partly filled with oil fit or other liquid.The gas under pressure s...

The pipes 22 are preferably arranged in a row extending transversely oithe furnace, this row being at right angles of the general direction ofmovement oi the glass through the furnace. The pipes as shown are placednearer to the discharge end than the receiving end of the tank. It willbe seen that with a row of. pipes thus arranged and discharging asbubbles at short 'intervals, there will be a continuous upward movementof 'these bubbles, all in a substantially vertical plane and distributedat short intervals throughout the area of the glass within such plane.Thus there is produced a rising curtain of molten glass which is drawnupwardly with the'gas bubbles. ,A'sa result the metal which wouldordinarily travel along or adjacent to the bottom of the durnace-ismoved upward toward the surface where the higher furnace tempera-1 tureand greater fluidity oi the glass allow a comparatively rapid release ofthe entrapped gases, thus materially aiding in the filling process.

At the same time this movement oi'the glassjn the form or a rising.curtain serves to prevent a rapid'and continuous movement of the.surface glass and batch' materials directly from the charging end of thefurnace to the conditioning chamber it. The action is suchasto preventstagnation of the lower. strata oifslass in the iurnace and to insurethe thorough mixing of the materials. during the melting process whiledirecting the convection-currents and preventing the formation of cords,streaks and other conditions which would result in lack or homogeneity.in the final product. The controlled circulation containers into theliquid-therein. The rate at which. the gas flows is clearly shown. byits bubbling through liquid in said containers. Pressure gauges 43individual tothe pipes 42 indicatethe pressure. Valves @6 in the pipes42 provide means for throttling or cutting oil the flow through anselected line 22. A gauge 46 in dicates the pressure in the manifolds.

The rate or flow of gas may be varied through.- out a rather wide rangeIn coerclal operations I have obtained satisfactory resultsiwith ratesor new ranging from as low as air: bubbles per minute released from eachline, up to ice or more. The most satisfactory rate 0! flow depends uponvariable factors met with in the melting and fining operations such assize of the tanlgdepth of the glass, composition 02 the glass batch,temperatures at which the glass is drawn from the furnace and otherfactors. jg;

Modifications may be resorted to'within the spirit and scope of myinvention. Y I claim:

.1. The method oifproducins a localized movement or molten mefildm'abody of said metal which'comprises intro .3. 8 gas bubbles into said"ass-2,2

ward and upward movement of the glass at a greater depth, andrestricting the application of said gas to said single line. a I 5. Themethod of melting and refining glass which comprises introducing glassbatch material into a melting and refining tank at one end thereof,applying heat to the upper surface of the batch ing the glass in thevicinity of said planefree from like forces and in a comparativelyquiescent condition whereby asheet or curtain of molten glass is definedand caused to flow in the said direction in which said forces areapplied.

of the tank, applying surface heat to the batch in the tank and therebymelting and fining the.

material as it advances through the tank, intro v to move upwardly fromthe bottom of said body through the molten glass in the form of asuccession of bubbles liberated at each opening and substantiallyconfined to the vertical plane of said line duringtheir upward movementthrough the body of glass, and"conflning the gas supplied through thebottom of the tank to said transverse line. I

4. The method which comprises introducing glass batch materials into atank furnace at one end thereof and causing the batch to move forwardthrough the tank, applying heat to the upper surface of the materialswithin the tank and thereby melting them and causing a more fluentcondition of the surfaceportions of the glass than of that at a greaterdepth and thereby tending to produce a comparatively rapid forwardmovement of said surface portions, applying gas under pressure to thebottom of the body of glass in'the tank at points distributed along thebottom of the tank in a single line extending transversely of the tankand confining the application of gas at the bottom of said body to saidline, and thereby causing gas bubbles to be liberated at said points andto rise through the molten glass in substantially a. single verticalplane and apply an upward force to the glass at pointsdetermined by theposition of said bubbles, applying a'retarding force to said surfaceportions of glass and accelerating the forof glass within the tank andthereby gradually melting the batch, withdrawing the molten glass fromthe opposite end of the tank as themeltin operation proceeds and therebycausing a slow forward movement of the mass of glass within the tank,and controlling thecurrent flow of glass within said mass by causing alocalized upward force to be applied to the glass at and in a verticalplane extending transversely of the tank, intermediate the ends thereofwith said plane located forwardly beyond the melting zone, and therebycausing the glass in and adjoining said plane to move upwardly and exerta pulling force on the lower strata of glass in the tank by which anaccelerated forward movement of the'glass along the bottom of the tankis produced while saidupwardly moving glass applies to the surfaceportion of the glass a force opposing the tendency to acceleratedforward movement of said surface portion under the influence of'the heatapplied thereto. I

6. The method of melting and refining glass which comprises introducingglass batch material into a melting and refining tank at one endthereof, applying heat to the upper surface of the batch of glass.within the tank and thereby gradually melting the batch, withdrawing themolten glass from the opposite end of the tank as the l meltingoperatio'n proceeds and'thereby causing a slow forward movement of themass of glass within the tank, and causing localized upward forces to beapplied to the molten glass at a multiplicity of points distributedthroughout a restricted area defined by a substantially vertical planelocated at an intermediate'position between the ends of the tank andforwardly beyond the glass melting zone, therebyv causing an upwardmovement of a curtain of glass at said plane accompanied by a forwarddrawing movement of the glass in the lower portion of the tank, theupwardly moving curtain of glass at the same time applying to thesurface portion of the body of glass a force opposing the tendency ofsaid surface portion of the glass to advance at a higher speed than thelower a Y strata of glass.

JOSEPH w. WRIGHT.

